This invention relates generally to miniaturized devices for controlled delivery of chemical molecules into a carrier fluid.
Accurate delivery of small, precise quantities of one or more chemicals into a carrier fluid is of great importance in many different fields of science and industry. Examples in medicine include the delivery of drugs to patients using intravenous methods, by pulmonary or inhalation methods, or by the release of drugs from vascular stent devices. Examples in diagnostics include releasing reagents into fluids to conduct DNA or genetic analyses, combinatorial chemistry, or the detection of a specific molecule in an environmental sample. Other applications involving the delivery of chemicals into a carrier fluid include the release of fragrances and therapeutic aromas from devices into air and the release of flavoring agents into a liquid to produce beverage products.
U.S. Pat. No. 5,547,470 to Johnson, et al., discloses automated devices for intravenous drug delivery in which plural pumping channels independently infuse drugs and fluid. These devices and delivery methods require that the drugs be carefully pre-mixed and stored in a liquid form. A liquid form can, however, reduce the stability of some drugs and therefore can cause undesirable variability of the drug concentration. It would be desirable to more accurately and reliably measure the amount of drug introduced into the intravenous carrier fluid, as well as to store the drug in a more stable form, for example as a solid.
U.S. Pat. No. 5,972,027 to Johnson discloses the use of porous metallic stents as vascular drug delivery devices. The devices reportedly deliver a drug from the porous structure of the stent to the surrounding tissue. Such devices, however, are limited in the number of drugs that they can deliver and are severely limited in the control of both the rate and time of drug delivery, as the delivery rate is governed by the porous structure, i.e. the drug is passively released. It would be advantageous to provide active and more precise control over the time and rate of delivery of a one or more of variety of drugs from the stents into, for example, the bloodstream passing through the implanted stent.
Microchip delivery devices, described in U.S. Pat. No. 5,797,898 and No. 6,123,861 to Santini et al., provide a means to control both the rate and time of release of a variety of molecules, such as drugs, in either a continuous or pulsatile manner. The devices further provide a means for storing the chemicals in their most stable form. These patents describe, for example, implanting the microchip devices by themselves into a patient for delivery of drug. It would be advantageous, however, to adapt the precise control of molecule release provided by these microchip devices into a variety of other applications.
Apparatus and methods are provided for the delivery of molecules to a site via a carrier fluid. The apparatus include microchip devices which have reservoirs containing the molecules for release. The apparatus and methods provide for active or passive controlled release of the molecules. The microchip devices include (1) a substrate, (2) at least two reservoirs in the substrate containing the molecules for release, and (3) a reservoir cap positioned on, or within a portion of, the reservoir and over the molecules, so that the molecules are controllably released from the device by diffusion through or upon disintegration or rupture of the reservoir caps. Each of the reservoirs of a single microchip can contain different molecules and/or different amounts and concentrations, which can be released independently. The filled reservoirs can be capped with materials that passively or actively disintegrate. Passive release reservoir caps can be fabricated using materials that allow the molecules to diffuse passively out of the reservoir over time. Active release reservoir caps can be fabricated using materials that disintegrate upon application of electrical, mechanical, or thermal energy. Release from an active device can be controlled by a preprogrammed microprocessor, remote control, or by biosensors.
The carrier fluids into which the molecules are released can be, for example, environments such as intravenous infusions, beverage mixtures, vascular fluids, and gaseous phases. In a preferred embodiment, the microchip device releases molecules that are contained within the reservoirs into a fluid that is delivered to a patient intravenously.
In another embodiment, the microchip device is integrated into a stent for the delivery of drugs, such as anti-restenosis drugs or such as pravastatin or other hypertension medications.
In yet another embodiment, the microchip delivers molecules, which can be in the form of, but not limited to aerosols, vapors, gases, or a mixture thereof, into a stream for either therapeutic or aesthetic purposes.
In general, the microchip provides a method for storing molecular species in their most stable form, which can be a solid, liquid, gel, or gas. Upon either passive or active reservoir opening, the one or more types of molecules are released into the carrier fluid in either a pulsatile or continuous manner. These methods will provide fine control over the amount of the molecules delivered as well as the time and rate at which delivery occurs. Additionally, the molecular delivery device will extend the shelf-life (i.e. stability) of the molecules offering new potential applications.